The outer skin layer (epidermis) contains both hydrophilic and hydrophobic substances, represented mostly by proteins-polysacharrides and lipids, which allow for slow but definite penetration of both water and lipid-soluble small molecule substances across the stratum corneum layer into the skin tissue. It is well established that the stratum corneum, forming the upper layer of the epidermis, is the structure controlling the absorption of various substances into the skin and tissues.
There are situations when the body or skin areas exposed to the environment can be contaminated with industrial or military toxic substances, which are soluble in lipids and lipid solvents. These substances will not penetrate across a hydrophilic layer if such a layer forms a continuity over the skin surface. A typical example of a high risk industrial toxic substance is parathion, which is used commonly as an agricultural insecticide. It is practically insoluble in water, thus it will not penetrate the hydrophilic layer of a hydrogel with high water content, but will be resorbed by unprotected skin. This can cause severe health risks to the exposed person. The same principle is applicable to several lipid-soluble toxic substances used as chemical weapons, e.g., vesicant mustard gas, or neurotoxic substance VX, which are oily substances that do not penetrate the temporary second skin formed by hydrophilic film.
The stratum corneum layer is also a barrier to disease organisms. It is known that infectious agents, such as viruses or bacteria, can inflict general infection and disease only if the skin integrity is impaired by cuts, rashes, or abrasions. This is especially important with human immunodeficiency viral (HIV) infections, which could be transmitted through skin-penetrating wounds inflicted by instruments, needles or from a manicure around the nail bed. Another possible entry for HIV, causing lethal AIDS, may be the exposure of broken skin to HIV through skin abrasion in the perianal region or as acute dermatitis (rash) when exposed to vaginal secretions during intercourse.
A major source of contamination is certainly through contact with the blood of AIDS patients. For this reason, rubber gloves were introduced in the state of New Jersey for the police force when dealing with potentially wounded criminals, in boxing, etc. This reflects the fear of the public of becoming contaminated by HIV. There is no doubt that the medical staff has the highest exposure risk not only to HIV, but to mycobacterium, tuberculosis or hepatitis B virus.
So far situations have been discussed wherein substances of a chemical or biological nature present in the environment could penetrate across the stratum corneum barrier into the body. However, the skin contains the sweat and sebaceous glands. Their distribution and concentration vary at different skin areas. The fingers and palm of the hand have relatively high densities of these glands, which are responsible for insensible perspiration or formation of the greasy sebum, a lipid-rich product that lubricates the surface of the skin and keeps the stratum corneum oiled. The volume of sweat-solution loss in an adult male varies between 0.5 and 4.0 liters per day. There are approximately 6000 sebaceous glands per square inch of the thick skin area. Besides various electrolytes (sodium, potassium, chlorine, etc.), sweat contains many water soluble substances, such as amino acids and vitamins. By sweating, the skin functions as an excretory organ. Both secretion products of sweat and sebaceous glands form an integral layer on the skin surface which leaves visible fingerprints when a smooth surface is touched, such as a mirror. There are professions, such as those which deal with the manufacturing of semiconductors, and work with optical lenses and similar objects, where these greasy marks will interfere with product quality. In these professions the employees use not only hair caps and facial masks, but also impermeable rubber gloves in order to minimize product contamination from fallout of skin scales or from body secretory products, represented mainly by oily products of the sebaceous glands. However, the relatively thick rubber gloves interfere with the fine tactile sensations needed for the work with small objects. Also, the impermeability of the rubber glove results in accumulation of the sweat and heat underneath the glove. Long term wearing of gloves may reduce heat loss to the point that the wearer suffers from thermal shock. There have been some attempts to use skin creams or collagen based lotions or creams to deal with the foregoing problems. These formulations do not form a hydrophilic protective layer, as fat is a common component of these cosmetic formulations. Thus, the protection achieved has been minimal.
Clearly, there is a need for an improved hand and skin protection system that does not involve rubber latex gloves. Gloves have been part of the clean room environment for many years and are known to be effective in reducing particular contamination from human hands. However, the gloves begin to generate particulates after several hours of use. Also, glove materials (e.g., latex nitrile, vinyl, etc.) vary in smoothness, thus affecting the ability of the manufacturer to clean the surface before packaging. Rough surfaces generally shed particulates and can transfer contaminant materials from one process to the other. Vinyl gloves are very smooth and easy to clean, however, they are an 80% dioctylphthalate (DOP) plasticizer. If a wearer of vinyl gloves presses a finger on a clean, smooth surface, fingerprinting will be observed because of the DOP being pressed out of the polymer.
Even the thinnest gloves reduce tactile sensitivity and the feedback that is needed to control delicate movement. Perspiration accumulates under the gloves, particularly with the no-powder gloves used in clean rooms.
In any case, glove technology cannot be used to reduce the shedding of skin flakes from the employee's face. If a mask is worn it may abrade the skin and increase particle generation. The response of employees to both masks and gloves is generally negative. One advantage of gloves is that it is difficult not to wear them properly. With masks, however, the situation is much different; it is difficult to get the employees to wear them properly.
It has been found that a major source of particles in the range from 0.2 microns to 5 microns in the ambient air is produced by flexing of human skin, especially skin between joints, such as finger joints, and from the eyelids. Minute particles of skin continuously flake off during normal movement of such skin. Consequently, obtaining extremely clean, particulate-free environment for manufacturing areas in clean rooms required for manufacture of high yield integrated circuits and the like requires provision of a means for preventing flaking of such skin particles from workers.
All of these problems suggest the need for a skin coating material that would stop contamination from oils and skin flakes while at the same time not being greasy or irritating to the skin. Naturally, the material must be easy to remove when the employee goes out on break, to lunch or home for the day.